Thermostat displays H2 and indicates low temperature detected at the thermostat (freeze warning)

Safety: If your home is at risk of freezing, protect plumbing and occupants first. No high-voltage work is required at the thermostat.

• Step 1 – Confirm actual temperature: Use a separate thermometer near the thermostat. If the whole home is cold, troubleshoot the heating system separately.
• Step 2 – Check for drafts: Remove the ecobee from its backplate and feel for cold air coming from the wall opening. Seal gaps with foam or putty, avoiding the electrical contacts.
• Step 3 – Inspect thermostat location: If installed on an exterior wall or near an unheated space, consider relocating the thermostat to an interior wall in a representative room.
• Step 4 – Verify heating operation: Set the ecobee to heat mode and raise the setpoint. Confirm the furnace or heat pump starts. If not, there may be a separate equipment fault.
• Step 5 – Replace thermostat if sensor is inaccurate: If ecobee reads much lower than actual temperature with no drafts or location issues, the internal sensor may be defective and the thermostat should be replaced.